This invention embodies improvements over the prior vacuum control valves represented by the Raab and Cobb U.S. Pat. No. 3,942,555; the Raab and Halstead U.S. Pat. No. 4,054,761; and the Raab U.S. Pat. No. 4,126,153. Each of these patents discloses a vacuum control valve which is combined with an electrical switch, for controlling a multiplicity of functions in an automotive heating and airconditioning system.
For example, the Raab and Cobb U.S. Pat. No. 3,942,555, entitled Electrical Switch and Fluid Control Device, discloses a device having three vacuum control valves, shown in FIGS. 12 and 13, which are operated by cam slots formed in electrical switching carriages, shown in FIG. 11. Each vacuum control valve, as shown in FIGS. 16 and 20-24, comprises a valve slider 216 mounted in a movable carriage 218. The slider 216 comprises a sealing member 220, made of silicone rubber, mounted on a backing plate 222 made of metal. A metal spring 230 is compressed between the backing plate 222 and the carriage 218, for biasing the sealing member 218 of the valve slider 216 into sealing engagement with a wall 210 in which valve ports 212 are formed.
The silicone rubber sealing member 220 of the prior Raab and Cobb patent is formed with passages or grooves 224 to afford selective communication between the valve ports 212. The silicone rubber member 220 is bonded or cemented to the metal backing plate 222.
This prior vacuum valve construction is complex and expensive, in that it involves several components, including the movable carriage, the silicone rubber sealing member, the metal backing plate to which the sealing member is cemented or mounted, and the metal spring. The bonding of the silicone rubber to the metal backing plate is a difficult operation which involves quality control problems. The assembly of the several components adds to the cost of the vacuum control valve.